"I think they're really starting to understand what the defensive front is capable of and the difference-maker you can be with the scheme of the defense," Carter said Tuesday.

They desire a new approach because last year's performance ranked as one of the worst in school history. The Boilermakers allowed 61 touchdowns, including 28 on the ground, 456 points and an average of 38 points a game — all program worsts. They also gave up an average of 235.4 rushing yards per game.

Opponents gashed Purdue's front line and reached the second level of the defense often. Part it was the inexperience up front the second half of the season and adapting to a new system.

However, the defensive line is physically stronger now. They understand what's being taught and how to apply the subject material. Improvement is a must, but how far the group advances remains to be seen.

"I think a lot of that has to do with coach Carter. Just the way he gets us right for practice," said Replogle, who added 30 pounds since the start of last season. "He knows you have to get your mind right every day. If our mind isn't right, he lets us know. The defense is counting on us to produce up front."

The line has maintained its consistent play even without Howard, who is sidelined with a groin injury. He suffered the injury last week, but coach Darrell Hazell projects the sophomore might return in the middle of next week.

Watson has filled in for Howard the last seven practices. The junior isn't as strong as Howard, but brings a different skill set to the nose guard and defensive tackle positions.

"I've been playing fast, thinking fast and playing strong. That's all I can do," Watson said.

It's clear Hazell and Carter have a core group of players they like on the defensive line. Russell needs a big season to prove he can reach the next level, and Replogle is poised to take the next step.

Keeping them healthy and productive will determine how much Purdue's overall defense improves this season.

"Those guys are starting to play well together," Hazell said. "If we can keep those guys together, we have a chance to be pretty good."